1. Be prepared. You can't be compelling if you're worried about what you're going to say next, says Nowak. If you have time, review the key points you wish to make before your meeting or presentation to ensure you're versed in the topic.

When there's no time to prepare, make a quick assessment of your audience and what will resonate with them. Talk about issues that matter to you: Tell employees about your passion for creating a great workplace and prospective investors about your vision for growth.

2. Shed the stoicism. "The moment we are in business we step into what I call the veil of the professional role," Nowak says. It's tough to be charismatic if your interactions don't have passion, humor, or some other element of emotion and human connection, he says.

If you're too buttoned-up and reserved, it's tough to truly connect with people. Nowak asks his clients to think about when they're at home with their children or out with their friends and when they're more "fired up" and to remember that feeling, tapping into it when they're in the office and need to motivate those around them.

3. Embody enthusiasm. Charisma has a physical component, as well, so pay attention to your body language. Notice how you stand when you're feeling comfortable and in control and practice that posture in everyday life.

Work on calming your breathing to appear more relaxed and confident. Smile and make eye contact. Slouching, anxious body language will undermine even the most passionate spoken message.

4. Be authentic. If it's not your style to make jokes or use hyperbole, then don't, says Nowak. Forcing yourself to adopt a style that isn't natural for you is only going to undermine your credibility, he says.

Get rid of rote, generic responses too. For example, Nowak helped one client increase employees' levels of engagement on conference calls just by changing her standard "that's great" response to more meaningful feedback. "It energized her and energized her listeners. It really is just retraining ourselves to look at how we interact with people on that micro level," he says.

5. Practice. It might sound odd to "practice" being charismatic, but Nowak says it's absolutely possible to increase your appeal and influence through repetition. The "muscle memory" of effective interpersonal communication is as real as that of physical activity.